Supplementary MaterialsMovie 1: Hh signaling in the adult zebrafish brain as revealed by whole brain light sheet imaging: transverse optical sections. heterogeneity in cell-cell signaling within the hypothalamic niche, with slow cycling Nestin-expressing cells residing among distinct and overlapping populations of Sonic Hh (Shh)-expressing, Hh-responsive, Notch-responsive, and Wnt-responsive radial glia. This work shows for the first time that Hh/Gli signaling is a key component of the complex cell-cell signaling environment that regulates hypothalamic neurogenesis throughout life. Significance Statement The extent, control, and consequences of adult neurogenesis in the hypothalamus are not well understood, despite the critical integrative role this conserved brain region plays in regulating basic metabolic and reproductive functions across vertebrate species. Here, we show that proliferation in the zebrafish hypothalamus continues into adulthood and begin to define the Elastase Inhibitor complex signaling environment of the hypothalamic niche that may regulate this adult neurogenesis. Using new conditional gene regulation tools, we show that the evolutionarily conserved Hedgehog (Hh)/Gli signaling pathway positively regulates hypothalamic neurogenesis during postembryonic development and into adulthood. These studies suggest a mechanism for the control of hypothalamic growth and tissue renewal, as well as the plasticity in neuroendocrine cell populations that is now linked to hypothalamic function. Introduction The hypothalamus is among the most ancient and evolutionarily conserved parts of the vertebrate brain (Nieuwenhuys et al., 1998), MADH9 regulating metabolism, circadian rhythms, autonomic function, and a wide range of behaviors linked to survival (Saper and Lowell, 2014). Dysfunction of the hypothalamus is associated with metabolic and reproductive impairments (Fliers, 2014; Saper and Lowell, 2014), and the hypothalamus is affected in many neurodegenerative disorders (Ishii and Iadecola, 2015; Winner and Winkler, 2015; Vercruysse et al., 2018). Growing evidence indicates that hypothalamic neurogenesis is required for hypothalamic function (Kokoeva et al., 2005; Migaud et al., 2011; Lee et al., 2012; Lee and Blackshaw, 2012; Xie and Dorsky, 2017). Life-long hypothalamic neurogenesis has now been documented in rodents (Ming and Song, 2011; Yoo and Blackshaw, 2018), sheep (Migaud et al., 2010), zebrafish (Wang et al., 2012; Schmidt et al., 2013), and likely humans (Pellegrino et al., 2018). Similar to more dorsal neurogenic zones, hypothalamic proliferation requires highly coordinated regulation of cell proliferation and differentiation within a discrete population of progenitors. Cell-cell signaling systems that regulate nervous system development such as the Notch, fibroblast growth factor (FGF), Wnt, Hedgehog (Hh), and bone morphogenetic (BMP) signaling pathways play a key role in controlling adult neurogenesis (Kizil et al., 2012; Petrova and Joyner, 2014; Anand and Mondal, 2017; Obernier and Alvarez-Buylla, 2019). Elastase Inhibitor Heterogeneity in both neural stem cell populations and in cell-cell signaling systems helps control the range of differentiated cell types that are produced in stem cell niches (M?rz et al., 2010; Chaker et al., 2016; Lim and Alvarez-Buylla, 2016; Ceci et al., 2018). Determining how this heterogeneity contributes to mind growth and adult neurogenesis remains Elastase Inhibitor a major challenge in the field. The highly conserved Hh signaling pathway settings cell proliferation, differentiation, and survival during embryogenesis (Varjosalo and Taipale, 2008; Briscoe and Thrond, 2013) and regulates neural stem cell proliferation in the mammalian hippocampus (Lai et al., 2003; Palma et al., 2005; lvarez-Buylla and Ihrie, 2014; Petrova and Joyner, 2014; Daynac et al., 2016). Misregulation of Hh signaling is definitely linked to neural tumors including glioblastoma and medulloblastoma (Wechsler-Reya and Scott, 2001; Raleigh and Reiter, 2019) and has been implicated in mediating Parkinsons disease symptoms and repairing nigrostriatal dopaminergic neurons (Gonzalez-Reyes et al., 2012). While Hh signaling offers been shown to be a key component of hypothalamic-pituitary (HP) axis development during embryogenesis (Kondoh et al., 2000; Guner et al., 2008; Blackshaw et al., 2010; Bergeron et al., 2011; Muthu et al., 2016), a role in the postembryonic and adult hypothalamus has not been recorded. The zebrafish mind, which maintains up to 16 proliferative zones throughout life, offers proven to be a powerful model for studying adult neurogenesis (Grandel et al., 2006; Schmidt et al., 2013; Anand and Mondal, 2017). Work in the zebrafish offers defined a role for notch signaling in the telencephalon (Chapouton et al., 2010, 2011; Rothenaigner et al., 2011) and uncovered a key part for Wnt signaling in hypothalamic neurogenesis, with.